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|A computer-generated rendering of the construction progress showing the purple pipes as part of a BIM.|
Advanced building information modeling (BIM) tools streamline a complex design-build pipeline project by delivering the right information at the right time.
As a “purple pipe” project, the Noman Cole Water Reuse Pipeline was designed for sustainability, using reclaimed water from the Fairfax County Noman M. Cole Jr. Pollution Control Plant for irrigation of local parks and for cooling purposes at a local energy-from-waste facility. Substantially completed in March 2012, the distribution of the reclaimed water required engineering design of pump stations, elevated water tanks and approximately five miles of large diameter (12- to 30-inch) pipeline through an urban corridor in the Washington, D.C., Metro area. Professional services firm Dewberry was tasked with designing and modeling the project.
Because the Noman Cole Water Reuse Pipeline was a design-build project, the schedule was critical and required construction to begin within 60 days of the notice to proceed. In addition to the timeline constraints, the alignment of the pipeline followed a complex terrain profile across major highways, multiple waterways, and under railroad and interstate highway bridges.
One of the most challenging goals of the project was to design the pipeline to prevent the need for relocation of any existing utility. The corridors contained a dense cluster of major gas transmission lines, sanitary force mains, telecommunication ducts, storm sewer, sanitary trunk lines, petroleum lines and other services. Any conflicts would be costly.
To significantly enhance the project’s workflow through rapid and accurate 3D modeling--even at the earliest stages of the project--Dewberry relied on Autodesk building information modeling (BIM) design tools.
Using Autodesk AutoCAD Civil 3D, Dewberry developed a design system with substantial intelligence built into the design process and final model. Dewberry was able to demonstrate a deep understanding of the project because of the information the team produced during the project’s proposal procurement phase. The conceptual visualizations provided context to design alternatives and allowed for informative decision making.
|A portion of the design corridor passing below Route I-95 in the Washington, D.C., Metro area.|
The project information model combined aerial survey data, subsurface utility designations, field survey data and proposed pipeline corridor modeling. As a design-build job, the project benefited from a dynamic model environment that assisted in quickly developing deliverables that matched the pace of an accelerated design, plan approval and construction schedule.
An additional benefit of the information modeling design process was the various output options of the proposed design, which included visualizations and geospatial data. Throughout the project, visual representations of the model were provided to the client and contractor to assist in communicating the design intent. For example, an export of the design model to a GIS format allowed for viewing of the design data on a mobile device during field visits.
The digital terrain data for the project’s five-mile corridor originated from three main sources: an aerial survey, a field survey and proposed design models. In areas where a higher resolution of information was necessary, such as adjacent to historic sites or environmentally sensitive areas, field survey data supplemented the aerial topography to provide high definition to specific project regions. Field survey data was also used for regions that were obscured to aerial topography, such as highly vegetated areas or beneath highway and railway bridges.
The aerial digital terrain model served as the initial surface for the information model. As field information was gathered, additional definition was added to the same surface model. The design profiles displaying the existing surface would dynamically update to represent the additional definition that was added to the surface model. This BIM process presented the current surface model at all times--instead of having to run profiles as information was added.
The digital terrain model helped Dewberry overcome challenges of working in a densely populated area. The continuous and rapid growth within the D.C. Metro area presents cases of concurrent design initiatives. For example, within the waterline corridor, there were proposed highway improvements as well as site development adjacent to the waterline corridor. These other design projects proposed significant modifications to the existing grade and required the development of additional surface models. The proposed surfaces were also represented in the design profiles, and the waterline profile was developed to accommodate future changes. Throughout the development of the waterline design, the proposed surface models were updated in the BIM model. The dynamic link of the surface model to the design profiles proved beneficial to the design process.
Beyond the benefits seen from the drafting perspective of a dynamic surface profile, the digital terrain model helped with the analysis and design of the proposed waterline. The geometry of the construction trench could vary dramatically because the proposed water profile varied in depth to avoid utility conflicts or reduce the number of high and low points. Furthermore, running a corridor through the model based on sloped trench side walls or sheeting and shoring provided another dynamic element to the limits of disturbance. However, within the BIM model, the daylight line of a sloped trench would adjust based on depth of the proposed waterline resulting in an accurate location of the limits of clearing and grading.
|Screenshot of corridor from BIM with relevant utility data linked to 3D content.|
A portion of the proposed waterline alignment fell within the limits of a six-lane divided highway, passing below a Route I-95 bridge and beneath a railroad bridge. In addition, the waterline’s corridor included major utility crossings of storm, sanitary, water transmission, petroleum, underground power and telecomm, gas transmission lines and sanitary force mains.
Subsurface utility consultants were able to provide horizontal locations of the non-gravity utilities. By modeling them as intelligent BIM pipe networks, the design profiles displayed crossing locations along the alignment at design depths. As test pit information was obtained at critical crossing locations, the utility model would be updated to reflect the field collected data, which would dynamically adjust the crossing depth in the design profile.
The information for gravity utilities, such as structure and pipe inverts for storm sewer and sanitary sewer, was collected through field surveys. Models of these systems were also added to the BIM file to accurately reflect crossing locations. BIM enabled crossing depths to adjust as the horizontal alignment was modified, preventing rework of continuously adjusting crossing location in the design profile and re-computing the crossing inverts.
The analysis tools within the BIM allowed multiple levels of conflict detection. The proposed waterline was modeled as a pipe network as well, which detected direct conflicts and 3D clearances of the pipe network. By analyzing the trench corridor model, it was possible to determine if there was potential to undermine utilities that were adjacent to the trench and subject to exposure from trench slopes.
Developing a project within the BIM ecosystem provides additional benefits beyond faster plan production. The modeled objects are generally displayed as 3D objects, but a significant amount of metadata is also embedded into the design objects themselves. This metadata, such as pipe material, wall thickness, slope, inverts and confidence levels, can be translated into various other data formats.
An engineered surface model contains coordinate data, which allows for orthographic photography to be correlated with the digital terrain model and drapes the photograph onto the surface, providing an additional level of context to the alignment design. The 3D visualization helped Dewberry share their vision with others. Specifically, the photographic information helped the firm demonstrate the limits and scope of the project to the public.
A 3D view of the design objects can be easily created by rotating the perspective of the model, which is traditionally viewed only in plan and profile; no additional effort is required. These quick screen shots of critical areas showed dense utilities areas or structure within the vicinity of the corridor.
|A screenshot from mobile device displaying the purple pipe alignment within the Google Maps application, which provides the ability to show the user’s location in context with the proposed design alignment.|
Another added benefit of BIM is the ability to access design data in the field on devices that connect to GPS and imagery. Proposed alignment data was exported to a cloud-based system that enabled the geometry to be shown on a mobile device that identified the designer’s current location in reference to the proposed alignment. This was beneficial when navigating regions of the project that had minimal reference points and when the large scale context benefited design conversations.
Exporting the AutoCAD Civil 3D pipe networks to GIS data using Autodesk MAP 3D allowed collected information to be viewed in a multitude of environments, including GIS applications and web-based views, as well as smartphone and tablet environments. The ability within AutoCAD Civil 3D to “round-trip” the data, converting GIS content back into intelligent pipe networks, allowed for the collected information to be located within a single repository and referenced into design models as needed.
The ability to develop an intelligent, data rich 3D information model of the entire alignment allowed for confidence in the proposed design by the designer, the contractor, the utility entities and the owner, and enabled the project to be constructed without a single utility conflict throughout the five-mile alignment.
As Dewberry begins its next major waterline design project, best practices developed from the Noman Cole Pipeline project and the continued advancement in Autodesk design tools provide an even richer BIM ecosystem for development. Software such as Autodesk Infrastructure Modeler provides early conceptual planning and analysis, bringing in large amounts of data that can easily be stylized through GIS attributes--further enhancing efficiency in early design phases. It also connects to proposed design data, creating a fluid and dynamic environment for viewing miles of pipeline corridor in what almost becomes a personal Google Earth.
Online systems operate as a repository for collected information with enhanced connections between survey and GIS data. In addition, linking property data to geographic locations allows for online navigation of project information in a cartographic visual context, as opposed to a traditional file and folder viewer. Multiple Dewberry offices are now able to view the same set of information on mobile devices through the cloud-based system. The mobile GIS tools provide metadata to be viewed on smartphones and tablets with geographic referencing, in addition to the geometric elements. The icons within an online map can include information about pipe data, test pit information or parcel data that can be accessed on a smartphone or tablet device. Additional applications such as Autodesk’s AutoCAD WS and AutoCAD 360 allow for viewing of raw design files in a mobile environment as well, without the need for data conversion.
Reclaimed water is often distributed with a dual piping network that keeps reclaimed water pipes completely separate from potable water pipes. In the United States, reclaimed water is always distributed in lavender (light purple) pipes to distinguish it from potable water. The use of the color purple for pipes carrying recycled water was pioneered by the Irvine Ranch Water District in Irvine, Calif.